I loved my Prius until...

That doesn't make sense unless the heater core is leaking. I don't understand how you're not getting heat if it's putting out 85-140 degree air at the vents. Something doesn't add up.

Did they test it outside in the subzero degree temps? If those readings are in their comfy shop, that doesn't really tell them anything does it?

 

if it is the core, maybe you can find a salvage and have a local mech install it.

 

A restriction in the heater core will not allow flow through it easily enough at low engine rpms. That could account for the difference in temp between idle and 2000 rpm. One thing to keep in mind is that there is an aux electric pump that pushes coolant through the core when the ICE is off, like at a stoplight.

Hopefully the dealer would make sure that the cooling system was completely full before making such a diagnosis.

 

I thought there was a known issue with some of the plenum doors actuators failing or sticking for this GEN Prius? Might want to look it up.

 

I agree that the possibility of the coolant pump not working fully needs to be looked at. Also, the coolant system may have air trapped, as it is known to be troublesome to get it completely purged. The heater core is the place where the last holdouts are trapped.

There are no verified reports of heater cores just going bad that I have read here, so I think it is pretty rare. (Someone let us know if that is not the case.) But there have been reports of those pumps going bad from time to time.

The Prius is subject to misdiagnoses at the dealers, so a second opinion is worthwhile if possible.

 

1. How low was the coolant in the radiator itself (not the overflow container)? How much coolant had to be added?
2. If the engine coolant pump leak is more than trivial, that pump should be replaced first. Look for a pinkish residue on the inside of the coolant pump pulley and on top of the air conditioner compressor.
3. A significantly leaking engine coolant pump will result in the radiator coolant level dropping below the very top of the radiator neck because the pump leak allows air into the system. The radiator coolant reservoir will not replenish the leaked fluid in that case.
4. As more and more air gets into the radiator, this air will eventually get into the engine coolant loop.
5. Air in the engine coolant loop will result in air getting into the heater core which prevents the heater core from properly operating. You can sometimes hear air bubbling around in that case.
6. There is an electric coolant pump whose job it is to circulate engine coolant to the heater core. This is needed because the Prius gasoline engine stops running from time to time during normal hybrid operation.

To summarize, I suggest that you first eliminate any leaks in the engine coolant system, by replacing the engine coolant pump. Then, ask the dealer tech to verify that the electric engine coolant pump is operating and then make sure that all air is purged out of the engine coolant loop. Finally, replace the heater core if the first two repair actions fail to get the heater to operate satisfactorily.

 

Boy, I would be VERY leery of having the dealer replace a heater core on a 2005 car. Heater cores last a long time. They live a pampered life inside the cabin of the car. There is virtually no reason it should have gone bad this quickly. I personally wouldn't go back to that dealer again. I think they are trying to take you.

Here are some things for you to know
1) heater cores are very reliable and usually only get replaced because of an accident (even that is very rare). The car usually wears out before the heater core.
2) heater cores can be fixed (if they're clogged, use lp air reduced to about 15 psi and increase the pressure as necessary), if they're leaking, they can soldered. Complete replacement is almost always unnecessary
3) I've been working on cars for 30+ years and the only time I've ever messed with a heater core was on a neglected 65 Ford Falcon. Even then, I fixed the original heater core.

Take a good look at what Patrick said above. That is excellent advice (as usual).

 

As with any major repair, whether to your car or to yourself, a second opinion is always smart when it can be done.

 

Big potential misdiagnosis red flag here! Make absolutely sure that the coolant is correctly topped off (in the radiator itself, not just the little plastic reservoir) - and the system "burped". You need to get that cooling system properly full and all the air out of it before spending $1200 on (possibly unnecessarily) getting the heater core changed.

 

Everyone has seemed to have missed an obvious question: does the OP park outside? If so......

Minnesota? Brrrrrrrrrrrrrr. Install a block heater or park in the garage if you have one.

 

Please post your vehicle mileage.

 

Not really - unless the engine has overheated to the point where it is starting to seize up.

The mpg results seem very reasonable given the ambient temps you drive in.

 

Just to let you know (and you may already know), the engine water pump is one of the ways dealers use to seperate money from their customer's wallets. Since you park in the garage, do you notice coolant on the garage floor? Can you crawl under the car and see remnants of coolant under the pump? I'm not saying your pump is not the problem but, I have read numerous threads of dealers ripping people off like this. Pls be careful and don't let them take you.

 

Well, if there is pink fluid on the ground, then your car is def leaking and the water pump is a likely culprit. I believe you are well on your way to fixing your "heater" problem.